A four-year plan of research training is proposed to examine oxygen tension and skin perfusion and their role in the prevention and treatment of wounds, specifically heel pressure ulcers. The significance of this proposed study is based on the increased incidence of heel ulcers in the clinical setting and lack of knowledge of the mechanism in heel pressure ulcer development. The overall purpose of this study is to compare and contrast heel skin oxygen tension in both legs before and after hip surgery when heels are subjected to external pressure and movement of legs is affected by pain. The specific aims of this study are to determine: 1) whether heel skin oxygen tension decreases from baseline in the first three days after hip surgery in elderly patients; 2) whether a controlled external loading pressure affects heel skin oxygen tension from baseline in the first three days after hip surgery in elderly patients; and 3) the relationship between heel skin oxygen tension and pain at baseline and for the first three days after hip surgery in elderly patients. Patients 65 years and older undergoing hip surgery will be recruited from the orthopedic units in acute care hospitals. Data will be collected preoperatively and then on the first, second, and third day after surgery. The study will provide a basis for future interventions to prevent heel pressure ulcers and lay the foundation for a program of research in wound healing in the elderly.